KR20140019806A - Method for supplying sequential power impulses - Google Patents

Abstract

The present invention relates to a method for providing a power pulse for a PVD sputtering cathode, which is subdivided into partial cathodes, in which case the power pulse intervals acting on the partial cathode are chosen to overlap, so that power withdrawal from the generator providing power is interrupted. You don't have to.

Description

Method for providing sequential power pulses {METHOD FOR SUPPLYING SEQUENTIAL POWER IMPULSES}

The present invention relates to a method for providing a power pulse.

Such power pulses are necessary, for example in connection with HIPIMS-technology. HIPIMS is High Power Impulse Magnetron Sputtering. This relates to a vacuum coating method, in which the material is sputtered from the cathode by a very high discharge current, thus ensuring that the sputtered material is highly anodized. When a cathode voltage is applied to the substrate to be coated at the same time, as a result, the anode ions generated by sputtering are accelerated in the direction of the substrate, thereby forming a high density layer. In this case, for example, power of 40 kW or more is used. However, sputtering of the material from the cathode is only possible within the range of short power pulses, since damage can be caused by overheating under longer action of power. The duration that can be sputtered at high power from the cathode must therefore be limited, which is the maximum allowable pulse duration.

The solution to this is to subdivide the entire cathode into partial cathodes and provide power sequentially to the partial cathodes. By this concept, a large number of cathodes insulated from each other (in this case, referred to as partial cathodes) are provided in the coating apparatus, so that a local discharge can be provided with a high discharge current. Possible implementations of this solution are described in German patent application DE 102011018363.

It is sputtered from the cathode at a high discharge current density during the power pulses acting on the partial cathode. At the same time the other partial cathode (s) can again be cooled before the power pulses act.

The inventor has confirmed that the pulse duration itself has a great influence on the layer properties of the layer formed by magnetron sputtering. Thus, there is a need for generators that can provide high power pulses that last very short and relatively long.

Generators generally provide a constant voltage at a fairly constant current. The generators are called "power supply" in English, meaning power supply. The situation is tricky when it comes to forming shorter power pulses of higher power as described above. For example, when a power supply providing 40 kW of power is connected, a time of about 700 μs elapses until a full power output is achieved with a commercially available voltage source. In cases where power pulses with shorter pulse durations are needed, such as this case, the available time elapses before full power supply. The power profile of this pulse is therefore unregulated and dynamic, and the sputtering method based thereon provides a layer that can be poorly reproduced and has suboptimal properties.

An object of the present invention is to provide a method for simply achieving a power pulse having a defined profile, in which case the duration of the power pulse should be able to be simply scaled over a wide interval.

According to the present invention, the above-mentioned problem is that the generator that provides the power when the power is diverted from the first partial cathode to the second partial cathode does not have to be shut down, but is executed without interruption of power drawing from the generator, whereby power is not increased again. To be avoided, the power pulse interval assigned to the first partial cathode is solved by slightly overlapping in time with the power pulse interval assigned to the second cathode portion.

During the overlapping time of the two power pulse intervals, the plasma burns only at the first partial cathode because the impedance associated with it is significantly lower than the impedance of the second partial cathode which has not yet been ignited. The plasma is ignited at the second partial cathode only when the first partial cathode is disconnected from the generator at the end of the first power pulse interval, which is substantially fast enough to allow continuous power draw from the generator. When a third partial cathode is provided, the power pulse interval assigned to the third partial cathode is slightly overlapped with the power pulse interval assigned to the second partial cathode, so that when power bypasses from the second partial cathode to the third partial cathode Power draw is not interrupted. In general terms, the power pulse interval assigned to the nth partial cathode is slightly overlapped with the power pulse interval assigned to the (n-1) th partial cathode, thereby powering from the (n-1) th partial cathode to the nth partial cathode Bypass avoids interruption of power draw from the generator. When power is bypassed to the last partial cathode and the power pulse assigned to that last partial cathode is provided, i.e., the power pulse cycle-also referred to as a group below-is completed, power withdrawal from the generator is stopped. Subsequent power interruptions are again used to cool the partial cathodes before the power pulses assigned to the cathodes are provided at appropriate intervals for the first partial cathodes.

Due to this process, however, at least the power pulses provided to the first partial cathode are in the temporal range of power increase of the generator, causing the power pulses to have an undesirable profile. Thus, according to a preferred embodiment of the present invention, power is first provided to the so-called dummy-cathode to provide power to the first partial cathode at least substantially during the power up interval. The power pulse interval assigned to the first partial cathode then slightly overlaps with the power increment interval, thereby preventing interruption of power draw from the generator when bypassing from the dummy-cathode to the first partial cathode, the first power pulse Substantially complete power is provided over a range of intervals. The above-described dummy-cathode may be implemented by, for example, a current circuit having an ohmic resistance, in which the corresponding voltage drops, and thus power is converted into heat.

As mentioned above, the power increase interval is in the range of 700 μs. The power provided to the dummy-cathode from the generator during this interval does not help the coating process, i.e., it is lost and forms a loss. This is not a problem when the power pulse cycle, i.e., the group interval is large compared to the power increment interval, and therefore only a small percentage of power loss. However, there is a problem when the power pulse intervals become small enough that the difference between the group interval and the power increase interval is noticeable. In this case, an unacceptable significant power loss occurs.

This is avoided by another preferred embodiment of the present invention. In short, the inventor has recognized that cooling of the partial cathode is not necessary at all when the power pulse intervals are short. In this case the second power pulse cycle follows the first power pulse cycle. In this case, the first power pulse interval of the second power pulse cycle (i.e., the second group) is slightly overlapped with the last power pulse interval of the first power pulse cycle of the first group, so from the last partial cathode to the first partial cathode Power bypass is possible without interrupting power draw from the generator. This prevents power loss due to the power increase interval and the discharge of power to the dummy-cathode in the case of the second group. Thus, the heat generated in the partial cathode allows the multiple groups to be aligned side by side until a substantial interruption of the power supply has to be made. In this group train, it may only be necessary once to direct power to the dummy-cathode during the power up interval at the start of the heat.

The invention is illustratively illustrated by sputtering techniques with reference to the drawings in detail.

FIG. 1 shows the situations corresponding to an embodiment divided into one row at partial cathodes 1-6 and into a loss interval 0 and a power pulse interval, where the horizontal axis is the time axis and the vertical axis is provided from the generator. It is power, and in the overlap region (eg td1) the power should be subdivided into two loads, which are not shown in the figure. Only three groups are shown in the figure.

In order to prevent cathode overheating, it is assumed that the total time during which power is supplied to the partial cathodes in the power train should be less than 100 ms:

(tpn-tdn) * N <100 ms = Tmax

Example 1

In connection with the first embodiment, the dummy-cathode is provided with power for 0.5 ms, that is, the loss interval tp0 is 0.5 ms, and of course includes a power increase interval of about 0.25 ms. Six partial cathodes in addition to the dummy-cathode are used. The power pulse interval is defined as tp1-6 = 0.2 ms and the overlap of power pulse intervals is set as td1-6 = 0.02 ms while power is supplied to one partial cathode in one group. A total of ten power pulse cycles are frequencyd, that is, ten groups form one column with loss intervals. Therefore, the total column spacing takes 10 * 6 * (0.2 ms-0.02 ms) +0.5 ms = 10.8 ms + 0.5 ms = 11.3 ms.

Thus, a 0.5 ms loss interval is compared to the time for a 10.8 ms power output used for coating. Compared to the power dissipation in the dummy-cathode, over 20 times more power is used for coating.

In the case where 40 kW is applied to the partial cathodes during the power pulse interval and the average sputtering power of 5 kw is preset for each partial cathode, the total column spacing is repeated at a frequency of 69.4 Hz, whereby the following equation applies:

(tpn-tdn) * N * Pmax * fr = 0.18 ms * 10 * 40 kW * 69.4 Hz = 5 kW.

This contrasts an average power loss of up to 0.5 ms * 40 kW * 69.4 Hz = 1.39 kW at the dummy-cathode. A repetition frequency of 69.4 Hz corresponds to a repetition duration of 14.4 ms. At the duration of the entire row interval of 11.3 ms, this means that a 3.1 ms pause is inserted between rows.

Example 2

With respect to the second embodiment the power pulse interval is reduced to 0.07 ms and the number of groups is increased to 100. Other parameters are maintained. Therefore, the total column spacing takes 100 * 6 * (0.07 ms-0.02 ms) +0.5 ms = 30 ms + 0.5 ms = 30.5 ms.

Thus, a loss interval of 0.5 ms is compared to the time for a 30 ms power output, which is used for coating. Compared to the power dissipation in the dummy-cathode, over 60 times more power is used for the coating.

If 40 kW is applied to the partial cathodes during the power pulse interval and the average sputtering power of 5 kw is preset for each partial cathode, then the entire column interval is repeated at a frequency of 25 Hz, where the following equation applies:

(tpn-tdn) * N * Pmax * fr = 0.05 ms * 100 * 40 kW * 25 Hz = 5 kW.

This contrasts an average power loss of up to 0.5 ms * 40 kW * 25 Hz = 0.5 kW at the dummy-cathode. A repetition frequency of 25 Hz corresponds to a repetition duration of 40 ms. At the duration of the entire row interval of 30.5 ms, this means that a 9.5 ms pause is inserted between the two rows.

Example 3

With respect to the third embodiment the power pulse interval is reduced to 0.05 ms and the number of groups is increased to 1000. Other parameters are maintained. Thus, the total column spacing takes 1000 * 6 * (0.05 ms-0.02 ms) +0.5 ms = 180 ms + 0.5 ms = 180.5 ms.

Thus the 0.5 ms loss interval is relative to the time for 180 ms power output, which is used for coating. Compared to the power dissipation in the dummy-cathode, more than 360 times the power is used for the coating.

In the case where 60 kW is applied to the partial cathodes during the power pulse interval and the average sputtering power of approximately 5 kw is preset for each partial cathode, the total column spacing is repeated at a frequency of 2.7 Hz, where the following equation applies:

(tpn-tdn) * N * Pmax * fr = 0.03 ms * 1000 * 60 kW * 2.7 Hz = 4.86 kW.

This contrasts an average power loss of up to 0.5 ms * 60 kW * 2.7 Hz = 81 kW at the dummy-cathode. A repetition frequency of 2.7 Hz corresponds to a repetition duration of 360 ms. At the duration of the entire row interval of 180.5 ms, this means that a 179.5 ms pause is inserted between the two sections.

Example 4

With respect to the fourth embodiment, the power pulse interval is kept at 0.05 ms, the number of groups is kept at 1000, and other parameters are also maintained. Thus, the total column spacing takes 1000 * 6 * (0.05 ms-0.02 ms) +0.5 ms = 180 ms + 0.5 ms = 180.5 ms.

Thus the 0.5 ms loss interval is relative to the time for 180 ms power output, which is used for coating. Compared to the power dissipation in the dummy-cathode, more than 360 times the power is used for the coating.

When not only 60 kW is applied to the partial cathode during the power pulse interval as in Example 3, but only 33 kw is preset in one partial cathode, and only about 5 kW of average sputtering power is preset in each partial cathode, The total column spacing is repeated at a frequency of 5.05 Hz, where the following equation applies:

(tpn-tdn) * N

* Pmax * fr = 0.03 ms * 1000 * 33 kW * 5.05 Hz = 5 kW.

This contrasts an average power loss of up to 0.5 ms * 33 kW * 5.05 Hz = 83 kW at the dummy-cathode. At the duration of the entire row interval of 180.5 ms, this means that only 17.5 ms of rest is inserted between the two rows.

As set forth in the foregoing embodiment, the method according to the present invention enables simple scaling of the precise definition of pulse duration, pulse height, pulse repetition frequency and pulse profile when the lossy power is almost gone and low. All of the above variables, which can be incorporated under the heading Scalable Pulse Characteristics, directly affect the properties of the layer formed during sputtering and especially with respect to HIPIMS-technology. Although the detailed description of the present invention describes the provision of power pulses in the context of sputtering techniques, the present invention is preferably applicable wherever relatively high power should be provided to the load in relation to the pulses.

Pavg Average Sputtering Power
Pmax Maximum Sputtering Power (Pulse Power)
tpn pulse length
tdn pulse delay
Number of N groups (N = 0 ... 500)
n channel number
(= Number of partial cathodes, n = 0 ... 6, n = 0 corresponds to dummy-cathode)
fr repetition frequency
tr repeat duration = 1 / fr

Claims (10)

A method of providing a power pulse having a scalable power pulse interval for operation of a PVD-sputtering cathode comprising a first partial cathode and a second partial cathode, wherein the maximum average power supply is preset for the partial cathode, The duration of power pulse intervals is preset, the following steps,
a) providing a generator having a constant power output, which is preset, preferably after at least a connection and after a lapse of a power increase interval
b) connecting the generator
c) connecting the first partial cathode to the generator such that power is provided from the generator to the first partial cathode;
d) separating the first partial cathode and the generator after the elapse of a corresponding corresponding first power pulse interval of the first partial cathode;
e) connecting the second partial cathode to the generator such that power is provided from the generator to the second partial cathode;
f) separating the second partial cathode and the generator after the elapse of a corresponding corresponding second power pulse interval of the second partial cathode,
In this case, the first power pulse interval begins in time before the second power pulse interval, and the first power pulse interval ends in time before the second power pulse interval.
In the above steps d) and e), the first power pulse interval and the second power pulse interval overlap in time, and all the power pulse intervals together form a first group so that the power output from the generator is equal to the first power pulse interval. And continues continuously without interruption from the beginning until the end of the second power pulse interval, wherein the second power increment interval does not appear. The method of claim 1, wherein the temporal overlap of the first power pulse interval and the second power interval pulse does not exceed x% of the power pulse intervals, or the duration of the first power pulse interval and the second power pulse interval is In other cases, the method is characterized in that x is less than or equal to 20, and preferably x is less than or equal to 10, not exceeding x% of the power pulse interval of shorter duration. The method according to claim 1 or 2, wherein the PVD-sputtering cathode comprises at least one other partial cathode, preferably a plurality of other partial cathodes, in which case the other partial cathode is generated according to steps e) and f). The power pulse intervals assigned to each other partial cathode connected to, separated from the generator, and returned in turn overlap in time with the power pulse interval corresponding to the immediately preceding partial cathode, and the first, second and other The power pulse interval (s) together form a first group that is not interrupted in time, so that during the group interval formed by the first group the power output from the generator continues uninterrupted and the second power increment interval does not appear. Characterized in that the method. 4. A method according to any one of claims 1 to 3, wherein the second group is related to the first group and within the second group corresponds to the first, second and optionally other partial cathodes corresponding to the first group. Power pulses within an overlapping power pulse interval are provided, in which case the second group is associated with the first group such that the first power pulse interval of the second group overlaps with the last power pulse interval of the first group. Wherein the power output continues from the generator continuously without interruption from the beginning of the first power interval of the group to the end of the last power interval of the second group, and the second power increment interval does not appear. 5. A method according to claim 4, wherein N groups are connected in sequence according to the conditions formalized for groups 1 and 2 in this case, where N is an integer> 1. 6. The number N of groups is preferably assigned at the maximum, but for each partial cathode n except for each overlapping tdn of all groups 1 to N for said respective partial cathodes. Characterized in that the sum of the power pulse intervals tpn is chosen so as not to exceed the maximum time of 100 ms. The method of claim 1, wherein the power output from the generator during the loss interval is not provided to the load used for coating, in which case the loss interval comprises at least a power boost interval and the loss. The interval overlaps the first power pulse interval of the first group, and the loss interval forms an uninterrupted column with the group. The method according to any one of claims 1 to 7, wherein the method according to any one of claims 1 to 7 is repeated several times, the generator is switched off during the rest period after the last power pulse interval of the last group, The resting period is characterized in that the time average power provided to the partial cathode is selected to a length corresponding to a preset value taking into account the resting period. A HIPIMS-method comprising a method according to any one of claims 1 to 8, comprising:
The preset power of the generator is at least 20 kW, preferably at least 40 kW, particularly preferably 60 kW. 10. The method according to claim 9, wherein the parameters are selected such that the time average power provided to the partial cathode is less than 10 kW, preferably 5 kW, in which case the discharge current density of the partial cathode intermittently and locally is preferably 0.2 A /. HIPIMS-method, characterized in that greater than 2 cm 2.

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